Amyloidosis is a devastating pathology associated with a growing number of diseases, including two of the most socio-economically impacting conditions of our time, Alzheimer's disease (Abeta amyloid) and type 2 diabetes (IAPP amyloid). Furthermore, cardiac amyloidosis in people over the age of 70 and in African American men is now recognized as a significant cause of morbidity. For these patients, there are few treatment options and no quantitative clinical imaging techniques for whole body detection of disease. Therefore, our long term goals are to develop amyloid-reactive peptides for the clinical detection and therapy of visceral amyloidosis in patients with these devastating conditions. During the first grant period it was shown that certain heparin-reactive small peptides specifically reacted with amyloid deposits but not with healthy tissues. This was demonstrated principally by using radioactively labeled peptides as imaging agents in mice with visceral AA amyloid as well as in mice with Abeta amyloid in the brain vasculature. Binding of peptides with amyloid was evidenced in SPECT images and micro-autoradiographs and was quantified by tissue biodistribution measurements. Recent data has now indicated that these peptides bind not only with highly-charged glycosaminoglycans that are present in all amyloid deposits but also the protein fibrils themselves, regardless of the precursor from which they are formed. We will leverage these novel findings to develop innovative molecular imaging agents and peptide therapeutics. The aims of this 5 year renewal proposal are to: Aim 1: Characterize and develop amyloid-reactive peptides, based on the structure of our lead peptide, p5, by generating variants for the quantitative detection of visceral amyloidosis. Aim 2: Evaluate the therapeutic potential o amyloid-targeting peptides in vitro and in vivo for preventing and removing visceral AA, IAPP, and ApoA2c as well as Abeta-derived amyloid deposits. Aim 3: Examine the fundamental processes underlying the binding of amyloid-reactive peptides with Abeta (1-40) and IAPP synthetic fibrils, as well as AA and ApoA2c fibril extracts. This will enhance our rational design and optimization of amyloid-targeting and therapeutic peptides. To achieve these goals we will combine advanced small animal SPECT/CT imaging, micro- autoradiography and biodistribution measurements for testing new peptides in mice with amyloidosis. Additionally, we will use a battery of in vitro assays that we have established to measure the therapeutic potential of the peptides and investigate the fundamental processes governing the interactions of these reagents with amyloid. These studies will lead to improved and effective molecular imaging radiotracers and companion therapeutics that can be translated and evaluated clinically in patients with these devastating diseases.